1. Fields of the Invention
The invention relates to over-voltage clipping diodes and more particularly to such diodes comprising P-N junction operating in the avalanche mode.
2. Description of the Prior Art
Those devices can be used for implementing protecting components operative against occasionnal electric overloads. They permit coverage of a large voltage range (from some volts to voltages in the range of 1,000 volts) and are generally adapted to the energy of the current overloads. Their very great response rate (some picoseconds) can also be used for cooperating with other security circuits during the first instants of an over-voltage. The dynamic resistance is relatively low in the avalanche mode, which is favourable to the limitation of a potential increase in the presence of over-currents, mostly when the avalanche voltage is low.
the protection diode or clipping diode aims to limit the applied voltage onto circuits to be protected, with respect to various electrical perturbations.
As a matter of fact, various electrical perturbations may occur at the terminals of an electronic network and damage or destroy the same. Those parasitic perturbations originate either from the electrical neighbourhood of the apparatus or from atmospheric phenomenons. For example, as regards a telephone line, lightning discharge will have to be absorbed by the clipping diode.
A P-N junction clipping diode, also often called PIN or PNN.sup.+ diode, indicating that this diode comprises outermost regions highly doped in the opposite type and an intermediate region forming the junction with the opposite type region, is substantially similar in its structure to a rectifying diode.
Thus, in the current practice, the diode manufacturers have often considered the over-voltage clipping avalanche diodes in the same way as the rectifying diodes as regards their connections, their mounting and their encapsulation.